The invention concerns a process for the covering of an open cut edge of a cardboard blank coated at least on one side, by means of a cover strip that may be folded around the cut edge and bonded to the surfaces of the cardboard blank by heating and pressing.
Known are foldable boxes or cup-like containers formed of a cardboard blank having a surface protected by a coating at least on the side which is to form the inside of the container. There exists, however, the problem that the cut edges, in particular, the inner cut edges, are not surface protected by a coating. The later-inserted contents of the cup or the box may thus penetrate through the open cut edge and into the coardboard. For this reason, in a known process of the afore-mentioned type (disclosed in DE-OS No. 21 02 001) a certain protection is provided at least for the inner cut edge which comprises a separate strip of a flexible, impermeable, heat resistant material, in particular aluminum, which is folded around the edge to be protected and tightly bonded to the material of the blank on both surfaces.
In the known process a strip of the protecting material is (i) unwound from a storage roll, (ii) guided parallel to the cut edge of a cardboard blank to be protected, and then (iii) folded. The strip has a width corresponding to the intended width of the later-covered strip, i.e., approximately the double width of the fold.
This known process has the disadvantage that it is not simple to cut a cover strip with precision dimensions. The apparatus employed in the process is rather bulky as the result of the process steps succeeding each other, while the strip is still connected with the storage roll. The cut edge of the cardboard blank must have a minimum length to permit the folding of the cover strip around it. Due to the fact that the cardboard blank must be guided parallel to the strip, the process is not applicable universally to different types of blanks. For example, open cut edges of conical cups cannot be covered in this manner.
It is an object of the invention to simplify the process and the necessary apparatus, and in particular, to render it largely independent of the type of the coardboard blank to be protected.